In the past, it has been required to obtain a copying machine of achieving high speed and energy saving. It has been developed an electrostatic image developing toner (hereafter, it may be simply called as “a toner”) excellent in low-temperature fixing property for that purpose. With respect to this kind of toner, it is required to decrease the melting point or the melt viscosity of the binder resin, and it was proposed a toner that improved low-temperature fixing property by adding a crystalline resin such as a crystalline polyester resin (refer to Patent document 1: JP-A 2008-40319, for example).
At this moment, it was also proposed to make toner mother particles to have a core-shell structure and to avoid the presence of the crystalline resin on the surface of the toner mother particles. However, due to the compatibility of the crystalline resin and the shell, there were produced deterioration of thermal storage property, and deterioration of toner fluidity caused by increased adhering property. Further, by uniformly forming a shell layer that is difficult to melt than the core particle, the wax became difficult to reach the toner surface. As a result, the fixing belt separation property of the thin paler became insufficient especially at high speed fixing.
On the other hand, from the viewpoint of cleaning property, developability, and transferability, it was proposed a technology of forming a convex portion on the surface of the toner mother particles by using a vinyl modified polyester resin (refer to Patent document 2: JP-A 2014-02309, for example). However, the property of the toner was insufficient as the toner containing the crystalline resin.